Drill/scredriver with impact mechanism



0a. 1, 1968 BURKHA RT ET AL 3,403,733

DRILL/SCREWDRIVER WITH IMPACT MECHANISM Filed Nov. 1. 1966 2 Sheets-Sheet 1 INVENTORSr- LARRYLBURKHART Oc 1, 1968 L. BURKHART ET AL 3,403,733

DRILL/SCREWDRIVER WITH IMPACT MECHANISM 2 Sheets-Sheet 2 Filed Nov. 1, 1966 LARRY 1.. BUR/(HART /Z 0715 0. H/TT and 34. P/IL/L 5. Moms I umns 73 0 88 78 63 80 WW ATTORNEYS United States Patent 015cc 3,403,738 Patented Oct. 1, 1968 3,403,738 DRILL/SCREWDRIVER WITH IMPACT MECHANISM Larry L. Burkhart, Edgerton, and Otis D. Hitt and Paul E. Troike, Bryan, Ohio, assignors to The Aro Corporation,

Bryan, Ohio, a corporation of Delaware Filed Nov. 1, 1966, Ser. No. 591,217 9 Claims. (Cl. 173-48) Another object is to provide a housing having a bit holder rotatable therein and adapted to slidably and nonrotatably receive a bit for coaction with a drill/screw or the like, a motor being provided in the housing for rotating the bitholder and an impact mechanism being also provided in the housing and including hammer means for delivering an impact blow to the bit in the holder.

Another object is to provide anvil means slidable in the bit holder for serving as a means to receive an impact blow from the hammer means and transfer it to the bit.

Still a further object is to provide control means for the motor and the impact mechanism which is operable in two stages, a first stage for effecting deliverance of the impact blow to the bit and a second stage operable to rotate the bit.

An additional object is to provide a trigger mechanism which includes a sequencing valve for first operating the impact mechanism and thereafter energizing the motor 'for rotating the bit holder.

Another additional object is to provide a type of impact mechanism which is pneumatically operated in such manner that upon operation a large volume of compressed air is dumped into a cylinder behind a piston of a hammer means so as to drive the hammer means rapidly forward at an accelerated rate whereby impact force is generated and delivered to the bit, such impart force being quite large in relation to the size of the hammer means and its piston.

With these and other objects in view, our invention consists in the construction, arrangement and combination of the various parts of our herein disclosed tool mechanism, whereby the objects above contemplated are attained, as hereinafter more fully set forth, pointed out in our claims and illustrated in detail on the accompanying drawings, wherein:

FIG. 1 is a side elevation on a reduced scale of a drill/ screw driver with impact mechanism embodying our invention.

FIG. 2 is a vertical sectional view thereof, the scale being approximately 'full size, and shows the tool being associated with a drill/screw for driving the same into sheet metal or the like;

FIG. 2A is a fragmentary detail of FIG. 2 showing parts of the tool in normal position before use of the tool is as in FIG. 2;

FIG. 3 is an enlarged sectional view on the line 3-3 of FIG. 2 showing a detail of the bit holder and the bit therein;

FIG. 4 is a similar sectional view with a trigger and sequencing valve in a first stage position and the impact mechanism delivering an impact blow;

FIG. 4A is an enlargement of the trigger and sequencing valve of FIG. 4 to show details more clearly;

FIG. 5 is a similar sectional view of a portion of FIG. 4 showing the parts in still another position wherein the trigger is in a second stage position and therefore deenergizing the impact mechanism and energizing the motor;

FIG. 5A is an enlargement of the trigger and sequencing valve of FIG. 5 to show detail more clearly; and

FIG. 6 is a sectional view of the trigger and sequencing valve as shown in FIGS. 4 and 5 but in a different position as assumed upon initial release of the trigger.

On the accompanying drawing we have used the reference numeral 10 to indicate a housing which has a handle 12 for holding the tool during the operation thereof. A cover plate 15 is provided for the front end of the housing. A bit holder 14 is rotatable in the housing 10 and the cover plate 15, and slidably and non-rotatably receives a bit 16 which may be retained therein by a retainer ball 18 in a groove 20 of the bit. The ball 18 is carried in a slot 22 of the bit holder 14 as shown in FIG. 3 and is held in position by a C-ring in an annular groove 24 of the bit holder.

This arrangement provides for limited sliding movement of the bit in the bit holder (compare FIG. 2 wit-h FIG. 2A) but non-rotation of one relative to the other because of hexagon-shaped portions of the bit in a similarly shaped bore of the bit holder as shown in FIG. 3.

A motor shown generally at M is provided (which may be of the vane type driven by compressed air) and ha a shaft 28 operatively connected with a gear on the bit holder 14 through planetary gearing shown generally at 30 which terminates in a drive shaft 32 geared to integral gear teeth of the bit holder by a gear 34 and an intermediate gear 36.

Impact mechanism is provided for the bit 16 in the form of a cylinder 38 in the housing 10 in which a hammer member 40 is reciprocable, a piston 42 being provided at the rear end thereof. A dump valve 44 controls the supply of compressed air to the cylinder 38 as will hereinafter appear.

The hammer member 40 is provided for delivering an impact blow to the bit 16. This is preferably accomplished through the use of an intermediate member designated generally at 46 which serves as an anvil to receive the impact blow from the hammer member 40 and transfer it to the inner end of the bit 16. The anvil 46 is in the form of a pin slidable in the bit holder 14 and normally biased forwardly by a spring 48 against a flange 50 of the pin. The forward position of the flange 50 is limited by a stop shoulder 52 of the bit holder. The inner end of the anvil 46 is slidable in a bushing 54, the outer end of which serves as a stop for a stop shoulder 56 on the anvil. A buffer ring 58 of neoprene or the like is provided for the hammer member 40 in its forward position shown in FIG. 4.

The dump valve 44 is slidable in a cylinder 60 and is normally biased to the forward position shown in FIG. 2 by a spring 62 interposed between the dump valve and a closure plug 64. The closure plug has a bore '66 in which an extension 68 of the dump valve 44 is slidable, and a system of vents and a port insures proper operation of the impact mechanism as will hereinafter appear, the vents being numbered 70 (in the plug'64) and 74 (in the cylinder 38), and the port being numbered 72 (in the cylinder 38). Suitable O-ring seals are provided for the hammer member 40. the piston 42, the dump valve 44 and the plug 64 as shown on the drawings.

A trigger button 76 is slidable in the handle 12 for operating a sequencing valve shown in normal position in FIG. 2 and in other positions in FIGS. 4, 4a, 5, 5A and 6. The sequencing valve comprises a stationary sleeve 78 in which is slidable a sleeve valve 80, a valve stem 82 being connected with the button 76. and slidable through a bore of the sleeve valve and terminating in a poppet head 84. The sleeve 78 is retained in position by a disc 86 (pinned at 88) through which the stem 82 slides, and a spring 90 is interposed between the disc 86 and the inner end of the trigger button 76. Suitable O-ring seals are provided for the sequencing valve as best shown in FIGS. 4A, 5A and 6.

At the lower end of the handle 12 is a compressed air supply fitting 92 as shown adapted for connection of a compressed air supply hose therewith for supplying air under pressure to passageways 94 and 96. The passageway 96 leads to large inlet ports 98 for the cylinder 38 as best shown in FIG. 4, and the upper end of a bleed passageway 51 leads from the cylinder 60 between the dump valve 44 and the plug 64. The passageway 94 supplies compressed air to a port 73 in the stationary sleeve 78 and the lower end of the bleed passageway 51 communicates with the rear end of the stationary sleeve 78. The sleeve 78 also has a port 53 communicating with an inlet passageway 83 leading to the motor M.

The sleeve 78 is provided with ports 55 which communicate with an exhaust pasasgeway 57 in the handle 12 and its lower end is provided with an exhaust fitting 59 having a suitable noise reducing screen associated therewith. The upper end of the exhaust passageway 57 communicates with the exhaust from the motor M.

The slide valve 80 is provided with ports 61 and an annular groove 63 which also enter into the operation of the sequencing valve as will hereinafter appear.

PRACTICAL OPERATION With the increasing use of drill/screws (self drilling and tapping screws) new production assembly techniques are being employed. One limitation to the use of such screws is imposed by the tools now available for use in assembly operations. One such limitation is that drill/ screws tend to lead 01f from the place where the screw is desired to be driven. This is a common problem encountered in starting drills on plane surfaces. For this reason locations for drilling are usually struck with a center punch before the drilling operation. Centerpunchin of locations for drill/ screws defeats the purpose for using this type of fastener and that is the economy brought about by elimination of extraneous assembly operations.

It is apparent therefore that a means to combine the center-punching and screw-driving operations into a single one would be beneficial. We have therefore devised the herein disclosed tool which initially delivers an impact blow against the screw as it is held in position to be driven, thus producing an action similar to that of a center-punch before the drill/screw is rotated for drilling, tapping and driving the screw to its final position of assembly.

Our tool is operated by first engaging the bit 16 with the head 65 of a drill/screw 67 havin a drilling and tapping point 69 with the screw in position against the work 71 which as illustrated in FIG. 1 may be sheet metal or the like. The tool presses the point 69 against the sheet metal at the point where the screw is to be inserted and the pressure of the bit 16 against the screw causes the bit to be forced inwardly relative to the housing against the bias of the spring 48 as shown in FIG. 2. FIG. 2A shows the normal position of the bit with respect to the bit holder with the spring 48 expanded and the flange 50 against the shoulder 52. In FIG. 2 the housing 10 (manipulated by the operator grasping the handle 12) is exerting thrust on the bit 16 through the bushing 54 and the stop shoulder 56 on the anvil 46. The inner end of the anvil is now in a projected position (relative to FIG. 2A) to be struck an impact blow by the hammer member 40.

The trigger button 76 is now depressed through two stages of operation. The first stage of operation is shown in FIG. 4A wherein the poppet head 84 is off its seat at the right hand end of the slide valve 80. This stage accordingly results in the bleed of air from the cylinder 60 through the bleed passageway 51, past the poppet head 84, through the bore of the slide valve, through the ports 61 (which are at this time in alignment with the ports 55) and to the exhaust passageway 57, as shown by three arrows a in FIG. 4 to discharge to atmosphere through the exhaust fitting 59. Since we are now bleeding air from behind the dump valve 44, and air is supplied to it from the passageways 94 and 96 through the inlet ports 98, the dump valve moves from the position of FIG. 2 to the position of FIG. 4 so that air is dumped from the ports 98 into the cylinder 38 behind the piston 42 for driving the hammer means 40 rapidly forward at a high rate of acceleration to deliver a very effective impact blow against the anvil 46 and then through it to the bit 16 as shown in FIG. 4. Such impact causes the point 69 of the drill/ screw to indent the sheet metal 71 so that the drill/screw will not lead off from the desired position upon rotation thereof when the motor M is subsequently energized. As the hammer means 40 moves forwardly and displaces air in front of it, such air is exhausted through the vent 74 which is covered by a suitable filter 77.

Continuing the depression of the trigger button 76 moves the sequencing valve into the second stage of operation shown in FIG. 5A wherein the ports 61 are moved out of alignment with the ports 55, thus cutting off the bleeding operation through the passageway 51 whereupon the dump valve 44 returns from the position of FIG. 4 to the position of FIG. 5 by reason of the compressed air from the passageway 96 and the inlet ports 98 on the front face of the valve building up the pressure behind it through a bleed passageway as shown by arrow b in FIG. 5, and the hammer member 40 is returned to the position of FIG. 2 by air through the port 72 from the passageway 96 acting. on the differential area as between the diameter of the piston 42 and the smaller diameter of a piston 41 at the forward end of the hammer means 40 in a reduced portion of the cylinder 38 in an obvious manner. Thus the impact mechanism delivers a single impact blow and is then rendered inoperative.

During such return motion, air behind the piston 42 is displaced through a bore 79 of the dump valve 44 and the vent 70 to atmosphere through another filter 81.

The second stage of operation of the sequencing valve as shown in FIG. 5A also energizes the motor M by reason of the annular groove 63 becoming aligned with the ports 73 and 53 so that compressed air from the passageway 94 can flow through the inlet passageway 83 to the motor M. Thus the first stage of operation of the valve delivers the impact blow as in FIG. 4 and the second stage returns the impact mechanism to normal position, and thereafter effects energization of the motor M so that the bit 16 may rotate the drill/ screw 67 for drilling, tapping and screwing the screw home. Once this is accomplished the motor M stalls and the operator thereupon releases the trigger button 76.

The release operation is also accomplished in two stages, the first stage being shown in FIG. 6 and the second stage being return to the normal position of FIG. 2. During the first stage operation as shown in FIG. 6, the poppet head 84 recloses against its valve seat on the right hand end of the slide valve to stop the bleed action from the passageway 51 to the passageway 57, thus preventing unwanted cycling of the impact mechanism. During both stages of valve return, a spring effects such return to the normal position shown in FIG. 2, thus causing shut-off of the supply of air to the motor M and the tool is ready for another drill/ screw driving operation.

From the foregoing specification it will be obvious that we have provided a tool that is extremely useful and timesaving in connection with the operation of driving drill/ screws or similar types of fastening devices. It eliminates the necessity of center-punching before placing the drill/ screw in position and automatically delivers an impact blow to cause center-punching prior to the delivery of compressed air to the motor for rotating the screw to drive it into position.

Some changes may be made in the construction and arrangement of the parts of our driving tool and its impact mechanism without departing from the real spirit and purpose of our invention, and it is our intention to cover by our claims any modified forms of structure or use of mechanical equivalents which may reasonably be included within their scope.

We claim as our invention:

1. In a tool of the character disclosed, a motor, a housing therefor, a bit holder rotatable in said housing, means for operatively connecting said motor to said bit holder for rotating the holder upon energization of the motor, a bit slidable and nonrotatable in said bit holder, hammer means slidable in said housing and having a normal position rearwardly therein, means for driving said hammer means forwardly in said housing to deliver an impact blow to said bit, an anvil interposed between said bit and said hammer means, means for biasing said anvil forwardly in said bit holder, and said anvil being provided with stop means in a forward position thereof.

2. A tool in accordance with claim 1 wherein a single manual control means is provided for said motor and said means for driving said hammer means, said control means being sequentially operable to first energize said means for driving said hammer means, and a second to energize said motor.

3. In a tool of the character disclosed, a motor, a housing therefor, a bit holder rotatable in said housing, means for operatively connecting said motor to said bit holder for rotating the holder upon energization of the motor, a bit slidable and nonrotatable in said bit holder, hammer means slidable in said housing and having a normal position rearwardly therein, pneumatic means for driving said hammer means forwardly in said housing to deliver an impact blow to said bit, control means for said motor and said pneumtaic means, said control means being operable in two stages, a first stage which releases a charge of air under pressure to said pneumatic means for driving said hammer means forwardly with acceleration and a second stage which energizes said motor.

4. A tool in accordance with claim 3 wherein said ham mer means includes a pneumatic piston, and said control means during operation in the first stage thereof effects supply of a large volume of compressed air behind said piston to drive the piston and thereby said hammer means forwardly at a rapid accelerating rate to generate a large impact force of said hammer means against said bit.

5. In a tool of the character disclosed, a motor, a trigger for controlling the energization of said motor, a bit holder, means for operatively connecting said motor to said bit holder for rotating the holder upon energization of the motor, a bit slidable and non-rotatably carried by said bit holder, anvil means and hammer means operatively associated with the bit in said bit holder, said anvil means being adapted to receive an impact blow from said hammer means upon energization of said hammer means and to transfer such impact blow to said bit upon energization of said hammer means, and control means for controlling the energization of said hammer means, said control means being operatively connected with said trigger to energize said hammer means upon initial depression of said trigger and to thereafter energize said motor upon further depression of said trigger.

'6. A tool in accordance with claim 5 wherein said control means effects the energization of said hammer means through a single stroke and then renders it inoperative before said motor is energized.

7. A tool in accordance with claim 5 wherein said hammer means includes a pneumatic piston, and said trigger during initial depression thereof efiects supply of a large volume of compressed air behind said piston to drive the piston and thereby said hammer means forwardly at a rapid accelerating rate to generate a large impact force of said hammer means against said anvil means.

8. A tool in accordance with claim 5 wherein said anvil means is slidable in said bit holder, is biased forwardly therein and is limited in its forward position.

9. A tool in accordance with claim 8 wherein buffer means is provided for said hammer means to arrest the hammer means before said anvil means reaches its forward limited position.

References Cited UNITED STATES PATENTS 2,403,675 7/1946 Mitchell 173-107 2,929,134 3/1960 Mosher 173104 3,171,286 3/1965 Stewart 173-48 3,349,651 10/1967 Turnbull et al. 14432 JAMES A. LEPPINK, Primary Examiner. 

1. IN A TOOL OF THE CHARACTER DISCLOSED, A MOTOR, A HOUSING THEREFOR, A BIT HOLDER ROTATABLE IN SAID HOUSING, MEANS FOR OPERATIVELY CONNECTING SAID MOTOR TO SAID BIT HOLDER FOR ROTATING THE HOLDER UPON ENERGIZATION OF THE MOTOR, A BIT SLIDABLE AND NONROTATABLE IN SAID BIT HOLDER, HAMMER MEANS SLIDABLY IN SAID HOUSING AND HAVING A NORMAL POSITION REARWARDLY THEREIN, MEANS FOR DRIVING SAID HAMMER MEANS FORWARDLY IN SAID HOUSING TO DELIVER AN IMPACT BLOW TO SAID BIT, AN ANVIL INTERPOSED BETWEEN SAID BIT AND SAID HAMMER MEANS, MEANS FOR BIASING SAID ANVIL FORWARDLY IN SAID BIT HOLDER, AND SAID ANVIL BEING PROVIDED WITH STOP MEANS IN A FORWARD POSITION THEREOF. 